JPH0595941A - X-ray tv apparatus - Google Patents

Abstract

PURPOSE:To provide a X-ray TV apparatus which enables the displaying of an object with a contract low and high as well on a screen on optimum conditions. CONSTITUTION:The maximum, minimum and mean of an image signal to be outputted from a TV camera 13 of an image tube 12 are detected to output the mean to an X-ray controller 16. Amplification characteristic and a gain of a non-linear type variable gain amplifier 14 are controlled based on the maximum, minimum and mean.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray television device used in the fields of medical treatment and the like.

[0002]

2. Description of the Related Art First, a simplified construction of a conventional X-ray television apparatus is shown in FIG. 2 and its operation will be briefly described. X emitted from the X-ray tube 10 and transmitted through the subject 11.
The line forms a visible image on the projection plane of the image tube (Image Intensifier = II) 12. This image is taken by the television (TV) camera 13 and displayed on the display device (CRT).
Etc.) 15 is displayed. Here, the brightness of a predetermined range on the projection surface of the image tube 12 is detected so that the image displayed on the display device 15 always has an appropriate brightness even if the X-ray transmittance of the subject 11 is different. A photo pickup 21 is provided inside the optical system 20, and an X-ray controller 16 appropriately determines operating conditions (tube current and tube voltage) of the X-ray tube 10 based on the brightness data.

[0003]

The feedback control of the above X-ray condition in the conventional X-ray television apparatus is as follows.
Since the average brightness is made constant within a predetermined range including the center of the screen, the X-ray image is adjusted so that the brightness of the image is appropriate for a flat (low contrast of X-ray transmittance) subject. When the line condition is set, when a subject such as a lung field having a large difference in subject thickness (high contrast) is projected, a thin portion causes whiteout (halation) or a thick portion causes blackout. On the contrary, if the X-ray condition is determined with reference to a region where the subject thickness is significantly different, when a flat subject is projected, the contrast is remarkably lowered and the details are destroyed. The present invention has been made to solve such problems, and an object of the present invention is to provide an X-ray that can display both a low-contrast subject and a high-contrast subject on the screen under optimum conditions. It is to provide a television device.

[0004]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above problems, controls the tube current and / or the tube voltage of an X-ray tube based on the brightness of an image formed on the image tube. An X-ray television device including an X-ray controller, comprising: (a) a non-linear variable gain amplifier provided between a television camera that captures the image and a display device that displays the image; and (b) a television. The maximum value, the minimum value and the average value of the image signal output from the John camera are detected, the average value is output to the X-ray controller, and the gain is applied to the nonlinear variable gain amplifier based on the maximum value, the minimum value and the average value. And an image adjusting circuit for outputting a signal.

[0005]

The image adjusting circuit (b) receives the output signal of the television camera, and detects the maximum value, the minimum value and the average value (of the luminance component) of the image signal within a predetermined range A in one screen. To do. The range A here may be the entire screen, but it is desirable to set the center part excluding the peripheral part of the screen in order to remove the part other than the image of the subject. Of the detected values, the average value is the same as the output from the photo pickup used in the conventional X-ray television device, and the average value is X.
It is sent to a line controller, where it is used to set the X-ray generation conditions (tube current and / or tube voltage) of the X-ray tube. However, only the setting based on this average value may cause blown-out highlights / black crushing on the screen of the display device or a flat screen with crushed details as described above. Therefore, in addition to the average value, the maximum value and the minimum value of the image signal are also used to properly adjust the gain of the image signal amplification in the non-linear variable gain amplifier (a). , Contrast) is set optimally.

[0006]

1 shows the basic construction of an X-ray television apparatus according to an embodiment of the present invention. The X-ray television apparatus of this embodiment is different from the conventional X-ray television apparatus shown in FIG. 2 in that the TV camera 13 attached to the image tube 12 is used.
And a display device (CRT) 15 for displaying the image signal, a non-linear variable gain amplifier 14 is provided, and the output of the TV camera 13 is taken in and the control signal is supplied to the X-ray controller 16 and the non-linear variable gain amplifier 14. Image adjustment circuit 1 for output
The difference is that 7 is provided.

The operation of the X-ray television apparatus of this embodiment is as follows. A subject 11 generated from the X-ray tube 10.
The X-rays that have passed through form a visible image on the projection surface of the image tube (II) 12. The TV camera 13 captures an image on the projection surface, generates a predetermined image signal, and sends it to the display device (CRT) 15 through the non-linear variable gain amplifier 14.

The image signal of the TV camera 13 is also sent to the image adjusting circuit 17, where the image adjusting circuit 17 selects from among the image signals within a predetermined range (which is referred to as AREA-P) in one screen. The maximum brightness and the minimum brightness are detected, and the average brightness of the image signals in another predetermined range (AREA-A) in one screen is calculated. As the predetermined range AREA-P here,
Except for the peripheral portion of the screen, it is desirable to set the range such that the subject image fits in a normal shooting state, but it is also possible to cover the entire TV signal for one screen. Further, if the predetermined range AREA-A is made equal to the range detected by the conventional photo pickup 21, it is convenient because it is not necessary to change the characteristics of the X-ray controller 16, but the maximum and minimum values May be matched with the range AREA-P for detecting.

The image adjusting circuit 17 sends the calculated average luminance signal to the X-ray controller 16. The X-ray controller 16 changes the tube current and the tube voltage of the X-ray tube 10 according to a predetermined procedure based on the control signal from the image adjusting circuit 17 as in the conventional case, and adjusts the intensity and wavelength of the output X-ray appropriately. Set to any value.
As a result, the average brightness of the transmitted X-ray image projected on the projection surface of the image tube 12 within the above-mentioned predetermined range is always kept constant.

However, when the X-ray transmissivity of the subject 11 is largely different (that is, when the contrast is very strong), whiteout or blackout occurs partially on the screen of the CRT 15.

Therefore, the image adjustment circuit 17 makes sure that the brightness on the screen of the CRT 15 at the maximum or minimum brightness portion of the image signal is within an appropriate range based on the detected maximum and minimum brightness values. , And controls the amplification characteristic and gain of the non-linear variable gain amplifier 14. A concrete example of this control is shown in FIG.
4 and FIG.

3 (a) and 4 (a) show the CRT on the horizontal axis.
6 is a graph in which the distance across the screen and the value of the image (luminance) signal are plotted on the vertical axis. 3 (b) and 4 (b) show the output signal a from the TV camera 13 in the first quadrant, the amplification characteristic curve of the amplifier 14 in the second quadrant, and the output signal of the amplifier 14 in the third quadrant (that is, , CRT15 input signal)
It is a graph which shows b. As shown in FIG. 3A, the X-ray image is relatively flat, and the maximum and minimum values of the image signal within the predetermined range AREA-P (in this case, AREA-A = AREA-P) are averaged. When it is not unbalanced from the value VAVE, as shown in the second quadrant of FIG. 3B, the amplification characteristic of the amplifier 14 is made substantially linear, and the average value VAVE of the output signal of the TV camera 13 is equal to that of the CRT 15. Input voltage VADJ (usually from white level 5
(A value of about 70%) and the gain of the amplifier 14 is set to be large so that the range of the upper and lower limit values of the image signal is widened. This adds contrast to the flat image and allows fine details to be clearly identified.

However, as shown in FIG. 4 (a), when black crushing occurs in a part (in this case, the central portion c) in the image before adjustment, X based on the average value of the image signal is obtained. If only the entire image signal is increased by adjusting the line conditions as shown in the first quadrant of FIG. 4B, the high-brightness portion will exceed the white level of the CRT 15 and whiteout will occur.
Therefore, based on the maximum value, the minimum value and the average value within the predetermined range, the amplification characteristic of the amplifier 14 is made non-linear (logarithmic or gamma characteristic) as shown in the second quadrant of FIG. As a result, the image on the CRT 15 has an appropriate range of V1 to V2 as shown in the third quadrant of FIG. However, the white level VMAX and the black level VMIN themselves may be used.)
It can be accommodated inside, and it becomes possible to satisfactorily observe the perspective image of the subject.

In the above embodiment, the X-ray shadow image taken by the TV camera 13 is CR as it is for simplification of description.
Although it is supposed to be displayed at T15, as shown in FIG.
The image signal generated by the V camera 13 is once digitized by the A / D converter (ADC) 30 and subjected to various image processing such as contour enhancement by the image processing circuit 31, and then the D / A converter (DAC) 32 again. The present invention can be applied in the same manner to a system in which an analog signal is returned to and displayed on the CRT 15 by.

[0015]

In the X-ray television apparatus according to the present invention, not only the average brightness of the image formed on the image tube but also the maximum and minimum values are taken into consideration for linear or non-linear amplification of the image signal. Therefore, it is possible to display an appropriate image with no overexposure or underexposure on the screen of the display device and with an appropriate contrast. For this reason, the operator does not need to spend time for the troublesome screen adjustment, and since the test exposure is not necessary, it is possible to shorten the imaging time and the exposure dose.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of an X-ray television device that is an embodiment of the present invention.

FIG. 2 is a block diagram showing a basic configuration of a conventional X-ray television device.

FIG. 3 is a graph (a) showing a shape of a screen signal in the case of a flat image and a graph (b) showing an amplification characteristic of an amplifier.

FIG. 4 is a graph (a) showing a shape of a screen signal and a graph (b) showing an amplification characteristic of an amplifier in the case of a shadow image in which light and dark are largely biased.

FIG. 5 is a block diagram showing the configuration of an X-ray television device that is another embodiment of the present invention.

[Explanation of symbols]

10 ... X-ray tube 11 ... Subject 12 ... Image tube 13 ... TV camera 14 ... Non-linear variable gain amplifier 15 ... Display device (CRT) 16 ... X-ray controller 17 ... Image adjustment circuit 20 ... Optical system 21 ... Photo pickup

Claims (1)

[Claims] 1. An X-ray television apparatus equipped with an X-ray controller for controlling the tube current and / or tube voltage of an X-ray tube based on the brightness of the image formed on the image tube. Non-linear variable gain amplifier provided between the television camera and the display device that displays the image, the maximum value of the image signal output from the television camera,
An image adjustment circuit that detects a minimum value and an average value, outputs the average value to an X-ray controller, and outputs a gain signal to a non-linear variable gain amplifier based on the maximum value, the minimum value, and the average value. Characteristic X-ray television device.